Drying process for wafers

Abstract

A drying process for wafers includes positioning the wafers to be dried in a cleaning device full of isopropyl alcohol (IPA) vapor and replacing moisture out of the wafers with the IPA vapor. Gas steam including the IPA vapor is exhausted from the cleaning device into a scrubber, and the scrubber has at least a solvent therein for dissolving the IPA vapor and an exhaust outlet for discharging gas mixture of the IPA vapor and the solvent. A flow rate of the solvent in the scrubber is adjusted to increase a concentration of the IPA vapor in the cleaning device and thus obtain better uniformity for drying the wafers.

Description

BACKGROUND OF INVENTION [0001] 1. Field of the Invention [0002] The present invention relates to a drying process for wafers, and more particularly, to a drying process to improve drying uniformity on wafers. [0003] 2. Description of the Prior Art [0004] During semiconductor fabrication processes, some metal ions, particles and organic compounds may remain on surfaces of wafers. Native oxides may also form on the wafers after cleaning, deposition, etching and conveying processes, degrading the quality of the semiconductor products. One or more cleaning processes are consequently employed to ensure the surface cleanliness of the wafers. [0005] In general, there are two types of cleaning processes: wet and dry. The wet cleaning process is wildly employed. For example, a resistor solvent such as ACT or EKC is often used to remove a resistor from a wafer after photolithographic and etching processes. Following that, cleaning solutions such as N-Methyl-Pyrolidone (NMP) and water are used...

AI Technical Summary

Benefits of technology

[0011] It is an advantage of the present invention that the amount of the dissolved IPA vapor in the scrubber increases with the increase of the flow rate of the solvent for dissolving the IPA vapor. As a result, the concentration of the IPA vapor exhausted from the exhaust outlet of the scrubber is accordingly reduced, and the exhaust rate of the IPA vapor from the exhaust outlet of the cleaning device to the scrubber is also reduced. Since the present invention method can lengthen the contact time of the IPA vapor with the wafer surfaces in the situation of not increasing the consumption of the IPA vapor, better uniformity and drying efficiency can be accomplished and problems such as resistance defects on the wafers and environmental impacts from organic contaminants produced by the IPA vapor can also be reduced.

[0012] These and other objects of the claimed invention will be apparent to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings.

Problems solved by technology

However, excessive rotational speeds can lead to damage to the electric devices on the wafer, and the wafer rotational speed is usually set to 3000 rpm for the spin drying method according to the prior art.

In this case, watermarks may be formed on the wafer and dissolved oxygen in the watermarks may further results in defects on the wafer since the rotational speed is insufficient.

Another problem of the spin drying method is the issue of static electricity.

During the high-speed spinning process of the wafer, charges may be accumulated on the wafer and may further attract particles in the air, thereby reducing the surface cleanliness of the wafer.

The IPA process does avoid charge accumulation on the wafer; however, it is not easy to replace the water droplets from within the trenches and the contact holes on the wafer with the condensed IPA.

But it is still difficult to take off the water droplets from within the trenches and the contact holes on the wafer.

Since the spin drying method is limited to rotational speed, wafer surface profile and static electricity, and has the problems such as the occurrence of the watermarks and the absorption to the particles, it is not suitable at all for being employed in some advanced semiconductor processes such as 0.18-micro or 0.15-micro processes.

In addition, both of the IPA vapor drying method and the Marangoni drying method have the disadvantages of being difficult to replace the water droplets from within the trenches and the contact holes on the wafer.

Therefore, it is necessary to lengthen the contact time of the wafer, the pure water etc. with the IPA vapor to cause a great consumption of the IPA vapor for both of the IPA vapor drying method and the Marangoni drying method to remove the water droplets from the wafer.

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